This invention relates generally to load responsive direction and flow control valves, equipped with positive load compensator, which while controlling a negative load interrupt pump flow to the motor, while the motor inlet is provided with fluid from the pressurized system exhaust.
In more particular aspects this invention relates to load responsive direction and flow control valves, which during control of negative load, while interrupting pump flow to the motor provide sufficient flow from pump circuit to the exhaust manifold circuit to maintain it pressurized under all conditions of operation.
In conventional pressure compensated load responsive valves the inlet flow requirement of the actuator, subjected to negative load, is supplied from the pump outlet flow. This common feature carries a number of serious disadvantages, since not only the pressurized fluid from the pump must be throttled down to a low pressure level, thus reducing the system efficiency, but also the capacity of the system pump to provide useful work is greatly reduced.
Those drawbacks can be overcome in part by provision of fluid control valves as disclosed in U.S. Pat. No. 3,804,447 issued to Masuda on Apr. 30, 1974. However, while those valves utilize actuator exhaust fluid for actuator inlet flow requirement when controlling negative loads, their principle of operation is based on series type circuit, in which excess fluid flow is successively diverted from one valve to the other and in which loads arranged in series determines the system pressure, instead of transmitting individual load pressure signal to the pump controls.